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Wire Bonding VS Flip Chip Bonding: How to Customize COB LEDs

PCBONLINE Team

Mon, Jun 13, 2022

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Wire bonding and flip-chip assembly are two bonding methods to interconnect ICs on ceramic PCBs. Sometimes, you will find standard COB (chip-on-board) integration solutions that can't meet the brightness requirement for your LED lighting products. In such a case, you will need to customize COB LED lights by wire bonding or flip-chip assembly. In this article, you can get an insight into wire bonding, flip-chip, and COB LEDs.

Part 1. What is a COB LED

COB is a LED light source solution that directly bonds multiple LED dies (or you can call them ICs) on ceramic plates or PCBs. The ICs usually are integrated at the center of the PCB in a rounded shape. When we power on the PCB, the ICs sheds even lighting.

COB LED PCB

For example, the above is a typical COB LED fabricated by the one-stop manufacturer PCBONLINE. The LED dies are flip-chip bonded on an aluminum nitride PCB. And they are sealed up with a protective glue layer. The glue can be in any color you wish.

Note
The ICs for COB LEDs are not those in shortage. The market supplies sufficient LED dies. We can source them easily and quickly.

You will need custom COB LED solutions when your LED lighting product requires very high brightness.

For example, the lighting devices underwater and on the sea require the brightness reaches 5000to 10000lumen. In contrast, standard LEDs on the market can't provide so much illumination.

You will also need custom LEDs if your lighting products have high requirements for color temperatures and chroma distribution. These products include lights on fishing vessels, in swimming pools, on yachts, etc.

To get lighting products mounted with custom LEDs, what do you need to do?

You need to design the PCB, buy ICs, order ceramic plates, and bond and seal up the chips on the plates. If this is only a module, you still need to assemble it on a ceramic or metal-based PCB.

Sounds a little bit complex? No worries, the EMS contract manufacturer PCBONLINE can provide you with one-stop COB LED solution.

Part 2. Wire Bonding VS Flip Chip

Wire bonding and flip-chip are two different methods of interconnecting the LED dies to the ceramic PCB. Their most obvious difference is whether gold wires are used or not. For a clear insight, please check wire bonding and flip-chip first.

What is wire bonding?

Wire bonding refers to interconnecting an LED die to the ceramic PCB using gold wires, as you can see below.

wire bonding

On one side of the IC, gold wires connect the positive electrodes of the PCB and the IC. On the other side, gold wires connect the negative electrode pads of the PCB and the IC. There is no solder paste. But the bonding is very stable.

When we power it on, the light sheds from the top of the IC.

What is a flip chip

Flip-chip bonding is similar to surface mount (SMT). And the IC is interconnected to the ceramic PCB with thermosetting solder paste. But the solder paste is electroplated at the bottom of the IC and becomes solder balls after reflow. Then the IC is picked and placed on the PCB. Under a compressing force, at about 300℃, the solder balls melt and cure to interconnect the IC and the PCB.

flip-chip bonding

When we power it on, the light sheds from the bottom of the IC and is reflected by a reflective film.


When the ICs are bonded on the ceramic PCB, whether by wire bonding or flip-chip bonding, we have to seal them up with a protective glue layer. The glue color is custom according to your product's lighting specification requirements.

flip chip

Wire bonding and flip-chip: which is better?

Wire bonding is a more expensive process than flip-chip and has more reliability. But both have pros and cons. Let's see a comparison table of the two COB LED bonding methods.

Wire bonding
Flip chip
Interconnection
Gold wires
Solder balls
Bonding cost
Higher
Lower
Reliability
Higher
Lower
Lighting source
On the top of the chips
At the bottom of the chips
Lighting efficiency
Higher
Lower
Thermal dissipation efficiency
Lower
Higher

We can't say which is better. You need to choose the die bonding method according to your specific conditions.

Part 3. Custom COB LED Solutions and Wire Bonding/Flip Chip Examples

The one-stop PCB manufacturer PCBONLINEprovides custom COB LED design and manufacturing solutions. We have a ceramic PCB factory and LED die wire bonding/flip-chip lines.

flip-chip COB LED assembly

For your project, we can provide free COB LED PCB designsaccording to your product's use requirements.

From PCBONLINE, aluminum nitride and alumina PCB (ceramic LED plates) manufacturing, wire bonding, flip-chip, MCPCB manufacturing, PCB assembly, box-built, and procurement of LED chips and other electronic components are available.

Please check two examples of COB LED projects we provided manufacturing for:

Example 1 - Custom RGBW Integration Solution (Wire Bonding)

The COB LED PCB below was designed by PCBONLINE's engineer for one customer. It's an RGBW (red, green, blue + white) LED light. We adopted the wire bondingmethod to bond the LED chips to the ceramic PCBs.

COB LED PCB designed by PCBONLINE

We provided the below solution to our customer:

We designed the COB LED PCB and chose the matching chips first.

Next, we manufactured an aluminum nitride LED plate (ceramic PCB) and wire-bonded the chips on the plate. A single LED module was manufactured, which could emit red, green, blue, and white light independently.

COB LED wire bonding

This RGBW LED module had a brightness of 8000 lumens. It can be surface mounted on another ceramic PCB or MCPCB.

We provided the customer with the sample as well as testing for free. When the customer checked and approved, we implemented the bulky production.

Example 2 - COB LED Light in a Composite Structure (Flip Chip)

Below is one piece of LED PCBs used for stage lights we manufactured for one customer.

In the center is the COB LED chips with the regular octagon shape. We flip-chip bondedthe chips on the white ceramic PCB module.

Then we embedded the ceramic PCB in the copper-based PCB.

flip-chip COB LED

Having seen the above wire bonding and flip-chip LED solutions, have you been inspired?

If you are interested in developing and manufacturing custom COB LED lights, feel free to contact the one-stop PCB manufacturer PCBONLINE by email at info@pcbonline.com.

Conclusion

Wire bonding is gold wires connection; flip-chip bonding is a solder paste connection. It depends on the product requirements and your budget in choosing which method for your custom COB LED fabrication. If you have any concerns about your COB design and fabrication, welcome to contact us online or by email.


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